Fuel cells are capable of efficient power generation despite the small size, and therefore have been drawing public attention and have been developed as power-generating devices of distributed energy resources.
A fuel cell uses a hydrogen gas as the fuel for power generation. At present, since there has not been general infrastructure for supplying a hydrogen gas, a fossil material supplied from the existing fossil material infrastructure such as a city gas and a propane gas is used to generate a hydrogen-containing gas, which is used as a fuel. Thus, a fuel cell is provided with a hydrogen generating device for generating a hydrogen-containing gas through steam reforming of the fossil material.
However, in a case where a fossil material is used, there is a problem that carbon monoxide (CO) from the material is contained in the generated hydrogen-containing gas. With a phosphorus acid-type fuel cell or a polymer electrolyte-type fuel cell, if a high concentration of carbon monoxide is contained in the hydrogen-containing gas, the Pt catalyst used in an electrode of the fuel cell may be poisoned by carbon monoxide to thereby substantially lower the output of the fuel cell. Therefore, a hydrogen generating device is provided with a carbon monoxide reducing section for reducing the concentration of carbon monoxide contained in the generated hydrogen-containing gas. The carbon monoxide reducing section includes a shift converter for subjecting carbon monoxide in the hydrogen-containing gas and a steam to a shift reaction using a shift catalyst, and a selective oxidation section for selectively oxidizing carbon monoxide contained in the hydrogen-containing gas having passed through the shift converter using a selective oxidation catalyst.
The carbon monoxide reducing section reduces the carbon monoxide concentration through a catalyst reaction, and the performance thereof is dependent on the catalyst temperature. Therefore, in order to effectively reduce the carbon monoxide concentration, it is important to control the catalyst temperature.
In view of this, Patent Document 1, for example, proposes a configuration for reducing the carbon monoxide concentration to be less than or equal to an intended concentration by controlling the catalyst temperature by air-cooling the hydrogen-containing gas after the reforming reaction. Patent Document 2 proposes a configuration in which the shift catalyst is divided into two portions and placed in series with each other, with a cooling section provided therebetween for air-cooling the hydrogen-containing gas.
[Patent Document 1] Japanese Laid-Open Patent Publication No. 2000-119004
[Patent Document 2] Japanese Laid-Open Patent Publication No. 2002-128507